This invention relates to the design of window systems utilizing the airloop principle to obtain high resistance to water infiltration.
A typical window system consists of a perimeter frame and at least one glass panel contained within the perimeter frame. The perimeter frame is secured to the edges of the wall opening. Each glass panel consists of a panel frame and a piece of glass secured inside the panel frame. The possible locations for water infiltration are the junctions between two adjacent window components. Sealants such as caulking or gasket are utilized at the above mentioned locations to prevent water leakage. In addition, a water drainage mechanism is provided at the bottom of the window system.
It is known in the industry that water infiltration is caused by three factors, namely, rain water running down on the exterior surface of the window system, positive differential air pressure due to wind, and imperfections in the sealant line. In the prior art systems, most of the sealant lines are used to perform two simultaneous functions, air sealing and water sealing. Perfect seals are required to prevent water infiltration. It is also known in the industry that perfect seals are extremely difficult to make and rarely last for any length of time. Therefore, first stage water infiltration within the window frame cavities is expected.
The water drainage system is provided to prevent second stage water infiltration into the building interior. However, the effectiveness of the drainage mechanism is reduced as the differential pressure increases due to the following reasons. The drainage hole is a passageway for air infiltration. The direction of air flow through the drainage hole is in the opposite direction of water drainage. Therefore, when a larger volume of air flows through the drainage hole due to a larger differential air pressure, it becomes more difficult for the water to drain out. Similarly, the degradation of sealant material due to aging may cause a larger rate of air infiltration leading to a reduction in the effectiveness of water drainage. Therefore, the watertightness of a window system is severely limited by the differential air pressure and aging.
In the case of operable windows, manufacturers normally offer a watertightness performance for a differential air pressure ranging from 6.24 psf (equivalent to a wind speed of 50 mph) to 7.5 psf when tested in accordance with ASTM E-331. In the case of fixed windows, manufacturers normally offer a watertightness performance for a differential air pressure ranging from 6.24 psf to 12 psf. Apparently, the above ranges of watertightness performance are inadequate for storm prone regions. Therefore, water leakage problems through window systems are rather common in the storm prone regions. To lessen the problem, a recessed window design is typically used to reduce the amount of water getting to the window.
The ultimate solution to the water leakage problem requires the elimination of dependency on the perfection of the sealant lines and the capacity of the drainage gutter. The objective of the present invention is to provide a window system that can tolerate imperfect seals anywhere in the system and that also can instantaneously drain any infiltrated water so that the watertightness performance can be maintained at a high positive differential air pressure.
In order to explain the working principles of this invention, the following terminologies are defined:
(1) Complex Seal: A sealant line being utilized to seal against both air infiltration and water infiltration.
(2) Air Seal: A sealant line being utilized to seal against air infiltration only (i.e. beyond the reach of water).
(3) Water Seal: A sealant line being utilized to seal against water infiltration only (i.e. pressure equalized).
From the above definitions, the following conclusions become obvious.
(1) To prevent water infiltration through a complex seal, the complex seal must be perfect.
(2) An air seal must be a dry seal located away from any possible water path in the system. Because an air seal is a dry seal, the air seal can be imperfect without causing water infiltration problem (equivalent to no rain condition).
(3) There must be near zero differential air pressure across a water seal. This means that the air space behind the water seal is pressure equalized to the exterior air pressure. Because there is near zero differential air pressure across a water seal, the water seal can be imperfect without causing water infiltration problem.
The window system of the present invention consists of a perimeter frame bordering the wall opening and at least one glass panel. A glass panel consists of a panel frame and at least one piece of window glass. In the case of multiple glass panels within a perimeter frame, a frame divider is sometimes used between two adjacent glass panels. The following locations are subjected to potential water leakage problem.
(1) Junction between the perimeter frame and the wall opening.
(2) Junction between the perimeter frame and the glass panel.
(3) Junction between two glass panels in the case of multiple glass panel system.
(4) Junction between the window glass and the panel frame or frame divider.
(5) Corners of the perimeter frame and the panel frame.
According to the present invention, pressure equalized airloops are provided along all the above-mentioned junctions to isolate the air seals from the water seals and an instantaneous drainage system is provided within the pressure equalized airloop region making water accumulation within the window system impossible. Multiple locations for air entry into the airloops are provided to eliminate the problem of high air flow rate through the water drainage holes.
The objectives of the present invention is accomplished by the airloop window system which enables the isolation of the air seals from the water seals.
Other details, objects and advantages of the present invention will become more apparent with the following description of the present invention.